Aestivation studies and the effect of imidacloprid on the subterranean life cycle of Laricobius spp. (Coleoptera: Derodontidae), biological control agents for the hemlock woolly adelgid

The hemlock woolly adelgid (HWA) Adelges tsugae (Annand) (Hemiptera: Adelgidae) is a non-native tree-killing pest of eastern hemlocks Tsuga canandensis (L.) and Carolina hemlocks Tsuga caroliniana (Engelman). HWA managers currently use an integrated pest management (IPM) approach that combines chemical, silvicultural, and biological control strategies to create a more sustainable and effective approach for managing HWA. Laricobius spp. (Coleoptera: Derodontidae) has been used as a biological control agent of HWA since 2003, and within IPM scenarios that include chemical control, there is potential for beetles to land on insecticide-treated trees and settle below their drip line for the subterranean portion of their lifecycle. Imidacloprid is the most widely used insecticide for HWA management and can persist along with its metabolites in the soil for up to 12 months post-application, which has been found to negatively impact soil microarthropods. During the subterranean portion of the Laricobius spp. lifecycle, adults are assumed to be undergoing aestival diapause, a crucial developmental stage triggered by hormones and seasonal changes to stop growth until conditions are suitable. Since there is limited knowledge on this portion of the Laricobius spp. life cycle and how imidacloprid and its metabolites impact this development stage, I propose to investigate the aestivation activities and impact of imidacloprid on the subterranean portion lifecycle of Laricobius spp. This will be carried out through measuring their metabolic activity, documenting burrowing depth by the use of 3D X-Ray imaging, and correlating imidacloprid soil concentrations to percent emergence.